Engines that are designed to burn one type of fuel are sometimes converted to burn an alternative type of fuel. For example, gasoline-fueled engines in forklifts, generators, etc. are oftentimes converted to burn propane and/or natural gas (commonly referred to as alternative fuels). Advantages of this conversion reduced exhaust emissions from and lower operating costs of burning the alternative fuels, and longer run times between refueling due to larger fuel tanks or connecting to utility gas pipe systems.
The conventional methods for converting conventional engines to burn a different fuel than they were designed for have proven problematic. For example, many conventional gasoline engines include a carburetor made of an aluminum block forming a venturi area, with a fuel inlet passageway extending through the block into the venturi area, and with a copper fuel inlet tube extending through the passageway. The venturi area creates a reduced pressure to draw the gasoline through the fuel inlet tube and into the venturi area of the carburetor. When converting such a gasoline engine to burn an alternative fuel, the gasoline fuel inlet tube is too small in diameter to deliver a sufficient volume of alternative fuel into the carburetor, so it generally cannot be used. So in one common conversion method, the gasoline inlet tube is removed, the gasoline inlet passageway in the carburetor block is drilled larger, and a correspondingly larger alternative-fuel inlet tube inserted into it. But this is a permanent modification to the carburetor, so it can never be practically used for gasoline again—it's an irreversible conversion process.
The other common conversion method includes inserting an adapter into the air stream ahead of the carburetor to introduce the alternative fuel to the carburetor. FIG. 1 shows one such prior-art alternative-fuel adapter 10 mounted between the air-inlet side of the carburetor 12 and the air filter 14 (i.e., the air cleaner assembly) of a gasoline engine 16. Inlet and outlet gaskets 18 and 20 are provided at the inlet and outlet sides of the adapter 10. The adapter 10 includes an appropriately-sized alternative fuel inlet 22 and a venturi 24 to draw the fuel 28 into the carburetor 12 for mixing with air 26. A common problem with using these adapters 10 is that, because of their thickness (commonly about 1¼ inches), they add overall size to the engine 16. So oftentimes the air filter 14 will not fit back on and one of the machine's structural vertical frame supports (not shown; typically positioned less than 1″ from the air filter assembly) must be cut to allow the needed additional clearance/space. In addition, because the air filter 14 is repositioned farther away, the air-inlet hose (not shown) oftentimes has to be lengthened or replaced. Furthermore, additional labor and cost is required to replace or modify the studs that hold the carburetor to the engine, for example, by replacing the existing studs with longer ones or by adding “stud extenders” to make up for the 1¼″ additional length. Moreover, an important issue for multi-fueled engines is the delivery of the alternative fuel 28 to the air stream 26 in such a way/position as to utilize the negative pressure signal necessary for zero governor regulators to function. Because the prior art adapters 10 introduce the alternative fuel 28 to the carburetor 12 at a position that is different from what the carburetor was designed for, the engines 16 typically do not run as well or efficiently as they were designed to.
Accordingly, it can be seen that there exists a need for a better way to introduce alternative fuels for combustion in engines. It is to the provision of solutions to this and other problems that the present invention is primarily directed.
The specific techniques and structures employed to improve over the drawbacks of the prior devices and methods and accomplish the advantages described herein will become apparent from the following detailed description of example embodiments and the appended drawings and claims.